Which is true about reaction rates?

Reaction rates are not related to spontaneity

Explanation:

A spontaneous reaction is one which occurs on its own or on some activation. Non spontaneous reactions are those which do not occur on their own and thus constant energy must be supplied to make them happen.

Reaction rate is dependent on the amount of reactants and the activation energy and not on the spontaneity of the reaction. Reactions with high activation energy are slow and reactions with low activation energy are fast.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).

they are all solids.